Thermal relay normally closed, with guillotine for opening



April 1960 J. c. MASSAR 2,934,622

THERMAL RELAY NORMALLY CLOSED, WITH GUILLOTINE FOR OPENING Filed June 9.1958 1? A 5 6 JULIUSC- N BY Jag M m- ATTORNEYS United States PatentTHERMAL RELAY NORMALLY CLOSED, WITH GUILLOTINE FOR OPENING Julius C.Massar, Van Nuys, Califi, assignor to Networks Electronic Corporation,Van Nuys, Caii'si, a corporation of California Application June 9, 1958,Serial No. 740,766

7 Claims. (Cl. 200-114) This invention relates to thermal relays ofsmall dimension, adapted to become operative in response to a rise incurrent above a selected critical value. More specifically, theinvention relates to that type of small dimension thermal relay aportion of which has the characteristics of a fuse and is included in acircuit which, when overloaded, will raise the temperature thereof tothe critical range; another portion of the relay providing a normallyclosed connection in a circuit (e.g. bridge circuit) which is separatefrom the fuse circuit.

It is to be understood that relays of this type have been hithertoproposed, and I do not claim as a broad invention, the concept of athermal relay embodying a fuse circuit and a separate relay circuit. Ageneral object of the present invention is to provide an improved relayof this type which provides a normally closed connection in a bridge orrelay circuit and has a means for mechanically breaking that connectionby a plunger which is released when the fuse element of the relay isactivated;

A further object is to provide a normally closed thermal relay embodyinga guillotine blade on a spring loaded plunger which is normally held ina retracted position by an overload current sensitive fuse element, theguillotine blade being adapted upon release of the plunger to be springdriven against a frangible conductor constituting a connection in therelay circuit, to sever said conductor and to thereafter positively holdthe severed fragments of the conductor in separated condition so thatthey cannot accidentally reestablish contact with one another. A furtherobject is to provide a thermal relay of the type indicated having hightemperature, shock, vibration, dielectric and electricalcharacteristics, all combined in a miniaturized envelope.

A further object is to provide such a relay which can be readilyfabricated in mass production, meeting an extremely difiicult problemthat has not been met with in prior attempts to fabricate such aminiature relay.

A further object is to provide such a thermal relay embodying electricalparts mounted in a glass envelope providing full visibility of theworking parts thereof, and having additionally, extremely highhermeticallysealed characteristics.

Gther objects and advantages will become apparent in the ensuingspecification and appended drawing in which:

Fig. 1 is an axial sectional view, on an enlarged scale, of a thermalrelay embodying my invention, showing the guillotine blade and frangiblerelay conductor in perspective relationto one another;

Fig. 2 is an axial sectional view of the same showing the guillotineblade in side elevation and the frangible conductor in end elevation;

Fig. 3 is an axial sectional view showing the parts in the relationassumed by them when the relay has opened in response to excessivecurrent;

Fig. 4 is a transverse sectional view taken on the line 4 4 of Fig. 3;

Fig. 5 is a fragmentary sectional view taken on the line 5-5 of Fig. 3;and

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Fig. 6 is a side view of my improved thermal relay, approximately actualsize.

Referring now to the drawings in detail, I have shown therein, as anexample of one form in which the invention may be embodied,'a normallyclosed thermal relay embodying generally an envelope structurecomprising a cylindrical tubular barrel A of heat resistant (e.g. Pyrex)glass tubing and headers B and B of composite metal and glass structureclosing the respective ends of the envelope; together with operativeparts hermetically sealed within this envelope and comprising generally:a fuse unit C at one end of the relay and a normally closed guillotineswitch D at the other end of the relay.

Before describing the details of the envelope structure, reference willbe made to the novel features of the guillotine switch D as combinedwith the fuse unit C, with which the envelope structure is combined toprovide a hermetically sealed casing.

The fuse unit C embodies an overload current sensitive yoke 15} havingspaced arms attached at one end of the yoke to the inner extremities ofa pair of conductor terminals 11 projecting through and anchored andsealed in the end cap B; the other end of the yoke 10 embodying a bight11 which is looped around a pin 12 anchored in a plunger 13, whereby theyoke 10 provides a tension link for holding the plunger 13 in aretracted position against the spring loading of a coil spring 14 whichbiases the plunger 13 for projection away from the end cap B and towardthe other end of the envelope.

The plunger 13 is of dielectric material, preferably a hard, rigidsynthetic resin plastic such as phenolic resin or other thermosettingresin of relatively unplasticized thermo-piastic material, i.e. anyselected resin having suit able dielectric strength and toughness,either acrylic, urea, vinyl, acetate, or other plastic resin material.It embodies a cylindrical body portion 15 having at one end an axialcavity 16 receiving the bight portion 11 of yoke 10 and a reducedcylindrical neck 17 piloted in the inner end of coil spring 14. Coilspring 14 is engaged under compression between the shoulder defined atthe base of neck 17 and the inner face of end cap B against which itsouter end is abutted. It is positioned by barrel A in concentric spacedrelation to the terminals 11, avoiding any electrical contact therewith.The current of the fuse circuit passes through the terminals 11 andthrough the yoke 10, whereby an overload of voltage or current willresult in the rupture of yoke 10 by melting, thus releasing the plunger13 for a switch opening action.

Guillotine switch D comprises a guillotine blade 18 formed as anintegral part of plunger 13 and projecting from the end thereof remotefrom the neck 17. Blade 18, at the respective sides thereof, is extendedto provide a pair of spaced fingers 1). The web portion of the blade 18,at its outer extremity, is provided with a nose 20 which may be ofchisel form as shown best in Fig. 5, for severing a line conductor wire21 which constitutes the frangible connector in the relay circuit.

The relay circuit includes a pair of terminals 22 extended through andmounted and sealed in the end cap B, projecting into the interior of theenvelope and having the connector 21 anchored to their inner ends andbridging therebetween as shown in Fig. l. The conductor 21 may beanchored by looping its ends around the respective terminals 22 andsoldering or welding the loops to the terminals.

In the retracted position of plunger 13, guillotine nose 20 is spacedaway from bridging conductor 21 a distance substantially less than thefull travel of plunger 13 which is limited by contact of fingers 19against the end cap B as indicated in Fig. 3. Thus at the time theguillotine blade contacts the bridging conductor 21, it will betravelling with sufficient speed to effectively sever the conductor 21without any possibility of stretching the wire and leaving it unsevered.As the plunger proceeds to its limit position shown in Fig. 3, the baseportion of blade 18 will enter between the fragments of conductor 21 andpositively hold them in separatedspacing as shown in Fig. 5.

Each of the headers B and B is of composite construction as shown in thedrawing, the terminals 11 and 22' consist in lengths of wire extendedthrough and mounted in the respective headers, and they have respectiveinner end portions projecting axially into interior of the envelope A.The inner end portions of terminals 22 are of sufiicient length toaccommodate the movement of plunger 13 to its limit position whereinfrangible conductor 21 has been severed. Conductor 21 is stretched undertension between the terminals 22, to facilitate its rupture by theguillotine blade 20 including a cylindrical plug 23 of high temperatureglass (cg. Pyrex) hav ing a pair of spaced parallel passages throughwhich respective terminals 11 or 22 extend; together with a metallicmounting ring of L-section including a cylindrical collar portion 2d anda radial flange 25 projecting outwardly from the outer end thereof; thecollar 24 encircling and being bonded to the cylindrical periphery ofplug 23 and being inserted into and bonded to the cylindrical inner wallof a respective end of barrel A; and the flange 25 being bonded to therespective end of barrel A. The terminals 11 are sealed into the plug23. As the means for bonding the mounting ring 24, 25 to the barrel Aand to the plug 23 respectively, I utilize the multiple layer bondingconnection disclosed more fully in the applications of Mihai D.Patrichi, Ser. Nos. 615,981 and 616,091 respectively, filed October 15,1956, for Electrical Resistors and Method of Fusing Metal to GlassArticles respectively. Briefly, such bonding connections (indicatedgenerally by numeral 26) comprise in general coatings of silver pastepaint applied and fused to both inner and outer end surfaces of barrelA, coatings of copper electroplated over the fused silver coatings,coatings of silver plated upon the mounting rings 24, 25, and coatingsof silver solder sweated into the interstices between the coatedmounting rings 24, 25 on the one hand and the coated surfaces of therespective ends of barrel A on the other hand.

In the operation of my improved thermal relay, the terminals 11' areconnected into a fuse circuit in which an overload will cause anexcessive current to be imposed upon the fuse link It} and to melt thesame so as to release the plunger 13 for spring loaded action; and theterminals 22 are connected into a relay circuit (e.g. bridge circuit) tobe protected against the effect of overloading the fuse circuit. In theevent the critical current level is reached, the plunger 13 will bereleased and will be projected by spring 14 against the frangibleconductor 21, severing the same and pushing aside the fragments thereofso as to open the relay circuit and positively maintain the same in theopen condition.

I claim:

1. In a miniature thermal relay: an envelope comprising a tubular barrelof high temperature glass and a pair or" headers closing and sealing therespective ends thereof, each of said headers comprising a central plugof high temperature glass corresponding to that of said barrel inexpansion characteristics, and a mounting ring of a metal that ismatched to said glass parts in expansion characteristics, interposedbetween and bonded to the respective glass parts at each end of theenvelope; an assembly of fuse parts in one end of said envelope,including a plunger slidably mounted in said barrel, a coil springengaged under compression between said plunger and an opposed header, apair of terminals extending through and sealed and insulated in the plugof said opposed header, and a fuse link attached under tension betweensaid terminals and said plunger and normallyholding thelatter in aretracted positionunder the load of said spring; and a normally closedswitch in the.

other end of said envelope, comprising a guillotine blade projectingfrom the end of said plunger remote from said coil spring, a pair ofradially spaced terminals extending through and sealed in the plug ofthe other header on respective sides of said blade, and a frangibleconnector wire anchored at the respective ends to the respective innerends of the last mentioned terminals in opposed spaced relation to theend of said blade and in transverse relation thereto, in a position tobe severed by saidblade upon projecti n of said plunger by said coilspring when said fuse link is severed.

2. In a miniature thermal relay: an envelope comprising a tubular barrelof high temperature dielectric material and a pair of headers closingand sealing the respective ends thereof; an assembly of fuse parts inone end of said envelope, including a plunger slidably mounted in saidbarrel, a coil spring engaged under compression be tween said plungerand an opposed header, a pair of terminals extending through and sealedand insulated in said opposed header and a fuse link attached undertension between said terminals and said plunger and normally holding thelatter in a retracted position under the load of said spring; and anormally closed switch in the otherend of said envelope, comprising aguillotine blade projecting from the end of said plunger remote fromsaid coil spring, a pair of radially spaced terminals extending throughand sealed and insulated in the other header on respective sides of saidblade, and a frangible connector Wire anchored at the respective ends tothe respective inner endsof the last mentioned terminals in opposedspaced relation to the end of said blade and in transverse relationthereto, in a position to be severed by said blade upon projection ofsaid plunger by said coil spring when said fuse link is severed saidblade including a pair of fingers projecting axially beyond the severingend thereof, in spaced embracing relation to said frangible connector,adapted to engage the opposed header to limit the projecting movement ofsaid plunger.

3. A relay as defined in claim 1, wherein said blade includes a pair offingers projecting axially beyond the severing end thereof, in spacedembracing relation to said frangible connector, adapted to engage theopposed header to limit the projecting movement of said plunger.

4. In a miniature thermal relay: an envelope comprising a tubular barrelof high temperature dielectric material and a pair of headers closingand sealing the respective ends thereof; an assembly of fuse parts inone end of said envelope, including a plunger slidably mounted in saidbarrel, a coil spring engaged under compression between said plunger andan opposed header, a pair of terminals extending through and sealed insaid opposed header and a fuse link attached under tension between saidterminals and said plunger and normally holding the latter in aretracted position under the load of said spring; and a normally closedswitch in the other end of said envelope, comprising a guillotine bladeprojecting from the end of said plunger remote from said coil spring, apair or" radially spaced terminals extending through and sealed andinsulated in the other header on respective sides of said blade, and afrangible connector wire anchored at the respective ends to therespective inner ends of the last mentioned terminals in opposed spacedrelation to the end of said blade and in transverse relation thereto, ina position to be severed by said blade upon projection of said plungerby said coil spring when said fuselink is severed, said blade includinga base portion which, in said limit position or" projection of saidplunger, is interposed between the severed fragments of said frangibleconnector to positively hold them separated from one another andpreventing their re-engaging one another.

5. In a miniature thermal relay: an envelope comprising a tubular barrelof high temperature dielectric material and a pair of headers closingand sealing the respective ends thereof; an assembly of fuse partsinzonecen'd of I.

said envelope, including a plunger slidably mounted in said barrel, acoil spring engaged under compression between said plunger and anopposed header, a pair of terminals extending through and sealed in saidopposed header and a fuse link attached under tension between saidterminals and said plunger and normally holding the latter in aretracted position under the load of said spring; and a normally closedswitch in the other end of said envelope, comprising a guillotine bladeprojecting from the end of said plunger remote from said coil spring, apair of radially spaced terminals extending through and sealed andinsulated in the other header on respective sides of said blade, and afrangible connector wire anchored at the respective ends to therespective inner ends of the last mentioned terminals in opposed spacedrelation to the end of said blade and in transverse relation thereto, ina position to be severed by said blade upon projection of said plungerby said coil spring when said fuse link is severed, said frangibleconnector consisting in a fine conductor wire stretched under tensionbetween the ends of the terminals to which it is anchored, whereby tofacilitate the severing thereof by said guillotine blade.

6. A relay as defined in claim 2, wherein said blade includes a pair offingers projecting axially beyond the severing end thereof, in spacedembracing relation to said frangible connector, adapted to engage theopposed header to limit the projecting movement of said plunger, whereinsaid blade includes a base portion which, in said limit position ofprojection of said plunger, is interposed between the severed fragmentsof said frangible connector to positively hold them separated from oneanother and preventing their re-engaging one another.

7. A relay as defined in claim 2, wherein said last mentioned terminalsdiverge from said other header toward said plunger and wherein saidfrangible connector consists in a fine conductor wire stretched undertension between the ends of said last mentioned terminals, whereby tofacilitate the severing thereof by said guillotine blade.

References Cited in the file of this patent UNITED STATES PATENTS710,056 Haskins Sept. 30, 1902 2,683,201 Miller et al. July 6, 19542,757,259 Cruse July 31, 1956 2,821,602 Hordechuck Jan. 28, 1958

